In a Direct Sequence-Code Division Multiple Access (DS-CDMA) system, since different signals have different propagation time delays and scramble code exists when using CDMA technique, spreading code used by respective signals are not completely orthogonal at reception. Interference caused by non-zero correlation coefficient is referred to as Multiple Access Interference (MAT). A Matched Filter (MF) or a Multi-user Detector (MUD) is commonly used to recover a signal without spreading and scrambling. A conventional matched filter may not efficiently suppress MAI. Multi-user detection may properly cancel the effect of MAI.
In the DS-CDMA system, a MUD may employ a Joint Detector (JD) method.
In a TD-SCDMA system, a Zero-Forcing (ZF) algorithm or a Minimum Mean Square Error (MMSE) algorithm is used for joint detection, the demodulated result thereof are as following:{circumflex over (d)}ZF=(AHA)−1AHAd+(AHA)−1AHn {circumflex over (d)}MMSE=(AHA+σ2I)−1AHAd+(AHA+σ2I)−1AHn 
Where, A represents a system matrix which is determined according to the spreading code and channel impulse responses of all user, d represents a transmit signal, n represents a noise signal, I represents a unit matrix, σ2 represents the power of the noise signal.
Since A corresponds to a received signal including all interference signals, A has a large number of matrix dimensions and the joint detection may need a large amount of computation. When there is a strong interference signal, the detection result is typically not accurate.